1. Field of the Invention
This invention is directed to an assembly for reducing the cost of energy required to maintain the environment within an industrial enclosure known as a controlled environment room, particularly but not exclusively, of the type designed for applying a powder coating to a plurality of work products disposed on a conveyer which continuously passes through the controlled environment room during the coating process. The assembly of the present invention is also directed to significantly restricting, if not prohibiting, the entry of particulate material or like contaminants into the controlled environment room, by subjecting the continuously moving work products carried on the conveyor, as well as the interior of the controlled environment room, to concurrent paths of positively pressurized, air flow. The assembly of the present invention thereby minimizes the escape of "conditioned" air from the controlled room and significantly reduces the energy costs associated with its replacement.
2. Description of the Related Art
The use of enclosures having a controlled environment is well known in industry and are often referred to as controlled environment rooms or controlled rooms. Such controlled rooms may be designed and structurally adapted for a wide variety of applications. However, common to virtually all of the various industrial applications is the attempted controlling of the interior environment of such controlled rooms or enclosures to the extent of controlling temperature, humidity, cleanliness and, in certain instances interior air pressure. While controlled environment rooms of the type referred to herein may include clean rooms, and even large, industrial size coolers or freezers, one common application of such controlled rooms is the application of powder coatings and/or paint, utilizing an electrostatic charge applied to each of a plurality of work products which may be mounted on a conveyor which continuously moves conveyor, with an opposite electrostatic charge provided to the powder coating or paint so as to facilitate application onto the work products. In this and other types of applications it is common for the controlled environment room to include at least two spaced apart and substantially opposing openings through which the moving conveyor, supporting the plurality of work products, passes. One of these openings is disposed so as to permit the entry of the plurality of work products into the controlled environment room and while the other opening is disposed to permit the exit of the work products from the controlled room, after the application of the powder coating thereon. In order to maintain the high quality standards expected, when products are processed in the above described manner, it is important that contaminant material from the environment or atmosphere surrounding the controlled room be restricted, if not prohibited, from entering the interior of the room, and thereby, interfering with the powder coating process. In addition, the maintenance of the temperature and humidity on the interior of the controlled room within certain preset or predetermined parameters is important, particularly because of the application of the electrostatic charge on the plurality of work products. In order to accomplish the required objectives in maintaining the interior of such processing rooms within acceptable industrial standards, air conditioning assemblies are used to deliver significant quantities of treated air to the interior of the controlled roms. The air conditioning assemblies also serve to maintain the temperature and humidity of such delivered air within the acceptable parameters. In addition, in an effort to reduce the entry of contaminants into the controlled room, the air pressure within the interior of such controlled rooms is maintained at a significantly greater level than the atmospheric pressure of the surrounding environment. Because of this increased interior air pressure, a continuous flow or quantity of air will pass out through each of the aforementioned work product openings. Contaminant material is, thereby, prevented or significantly restricted from entering through these work product openings, during the passage of the plurality of work products into and out of the interior of the controlled room. The recognized industry standard for the discharge of air from the interior of the controlled room is substantially one hundred and twenty (120') feet per minute. As such, a large volume of the treated and conditioned air being supplied to the interior of the controlled room by an air conditioning and treatment assembly is lost to the surrounding area or environment, on a continuing basis, and accordingly, in order to maintain an acceptable, high quality standard for powder coating applications, an additional supply of "make-up" air must be continuously returned to the controlled room in order to control the environment therein. However, the "make-up" air must also be treated and/or conditioned to have the same temperature and humidity characteristics as the air which is being continuously lost from the controlled room through the aforementioned work product openings. Therefore, in addition, to the problems associated with restricting the entry of contaminant material into the interior of the controlled rooms, an additional problem in this industry is the high cost involved in supplying the voluminous amounts of conditioned "make-up" air back to the interior of the controlled room.
In order to avoid problems of the type set forth above, attempts have been made to develop energy conservation systems for controlled environment rooms, particularly the type designed for powder coating applications of a plurality of work products. Specifically, in order to reduce the expense involved in returning "make-up" air to the interior of the controlled rooms, known attempts have utilized the application of negative air pressure to the areas immediately exterior of the work product openings in a controlled room. For example, one known assembly routes the air exiting the interior of the controlled room through such work product openings to a recycling assembly, which then reconditions the air and returns it to the interior of the room, instead of utilizing newly conditioned, "make-up" air. A drawback associated with this assembly, however, is that provision of the negative air pressure to the areas immediately exterior of the work product openings tends to accelerate the passage of contaminants, in the untreated air from the surrounding environment, toward the interior of the controlled room. More specifically, the existence of a negative air pressure is thought to have the effect of greatly accelerating the entry of contaminants in untreated air into an area where it is directly exposed to the work products, immediately prior to their entry into the interior of the controlled room, where the powder coating application would occur. This exposure to contaminated air at an accelerated rate and in greater quantities, could have the effect of depositing additional amounts of contaminants directly on the work products, just before they enter the controlled room. It could also have the effect of interfering with the application of an electrostatic charge to the work products, which may be needed in order to achieve a proper powder or paint coating on them as they pass through the controlled room. In addition, subsequent to an application of powder coating or paint within the controlled room, this known type of assembly would subject the work products again to the exposure of an accelerated flow of contaminated air as they exit through the corresponding work product opening. If, in fact, the drying or curing stage of the powder coating process was not complete at this point, such exposure could result in the depositing of additional contaminants thereon and in the forced removal of the powder coating and/or paint applied to the work product. Alternatively, if the application of the electrostatic charge to the work products was interfered with upon their entry into the controlled room, the quality of the coating would be lower and the drying or curing stage might take longer. In addition, the existence of the negative air pressure in the described, known assembly would appear to greatly increase the amount of conditioned air which exits the interior of the controlled room. Even if this increased volume of air is recycled, it must still have to be at least partially treated or conditioned again in order to raise or lower it to required temperature and humidity characteristics before it could be returned to the interior of the controlled room. The energy costs would, therefore, probably be increased because of the large quantity of recycled "make-up" air being treated and returned to the controlled room.
As set forth above, an important concern associated with controlled environment rooms such as large coolers or freezers is the escape of the conditioned air from the interior of the cooler/freezer rather than the entry of contaminants through a work product or other access opening formed therein. In this category of controlled environment rooms, it is well understood that the reduction of temperature and control of humidity within industrial size coolers/freezers involves extremely high energy costs. Accordingly, the escape of the conditioned air from such controlled rooms involves having to supply "make-up" air which has the same, significantly reduced temperature characteristics, and a significant increase in energy costs associated therewith. Attempts to reduce the escape of the conditioned air from the interior of this type of controlled room include the provision of plastic or like material curtains comprising a plurality of "ribbons" or "stringers" at the access opening to the cooler or freezer, which allows both personnel and products to pass therethrough. However, it is well known that such curtain-type of structures have been found to be less effective than desired at controlling the escape of air through the openings or portals which they attempt to cover. Another attempt to reduce the escape of conditioned air from the interior of such controlled rooms involve the use of "air curtains," which result in little or no savings in the energy cost associated with their operation for continuous or prolonged periods.
Therefore, there is a recognized need in the art associated with the utilization of controlled environment rooms or like enclosures for an improved assembly which can restrict, if not prevent, the entry of contaminated material into the interior thereof. Any such improved assembly should also be directed to reducing the energy costs associated with the maintenance of temperature, humidity, cleanliness and air pressure within the interior of such controlled rooms, such as by significantly reducing the amount of conditioned air escaping from the interior of the controlled rooms, and thereby, effectively eliminating the need for "make-up" air.